AFMC AFMC Solved Paper-2007

  • question_answer
    A stationary particle explodes into two particles of masses m1 and m2 which move in opposite directions with velocities v1 and v2. The ratio of their kinetic energies E1 /E2 is

    A) 1                                             

    B) \[{{m}_{1}}{{v}_{2}}/{{m}_{2}}{{v}_{1}}\]

    C) \[{{m}_{2}}/{{m}_{1}}\]                                

    D) \[{{m}_{1}}/{{m}_{2}}\]

    Correct Answer: C

    Solution :

    Key Idea: For a exploding body, linear momentum is conserved. From conservation of linear momentum, \[{{P}_{initial}}={{P}_{final}}\] \[0={{m}_{1}}{{v}_{1}}-{{m}_{2}}{{v}_{2}}\] or     \[{{m}_{1}}{{v}_{1}}={{m}_{2}}{{v}_{2}}\] or     \[\frac{{{v}_{1}}}{{{v}_{2}}}=\frac{{{m}_{2}}}{{{m}_{1}}}\]   ?(i) Thus, ratio of kinetic energies,\[\frac{{{E}_{1}}}{{{E}_{2}}}=\frac{\frac{1}{2}{{m}_{1}}v_{1}^{2}}{\frac{1}{2}{{m}_{2}}v_{2}^{2}}=\frac{{{m}_{1}}}{{{m}_{2}}}\times {{\left( \frac{{{m}_{2}}}{{{m}_{1}}} \right)}^{2}}=\frac{{{m}_{2}}}{{{m}_{1}}}\]


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